TY - JOUR
T1 - The equation of state of Al,H-bearing SiO2 stishovite to 58 GPa
AU - Lakshtanov, Dmitry L.
AU - Vanpeteghem, Carine B.
AU - Jackson, Jennifer M.
AU - Bass, Jay D.
AU - Shen, Guoyin
AU - Prakapenka, Vitali B.
AU - Litasov, Konstantin
AU - Ohtani, Eiji
PY - 2005/11
Y1 - 2005/11
N2 - We have determined the P-V equation of state of Al-rich H-bearing SiO2 stishovite by X-ray powder diffraction at pressures up to 58 GPa using synchrotron radiation. The sample contained 1.8 wt% Al2O3 and up to 500 ppm H2O, and had a composition that would coexist with Mg-silicate perovskite in a subducted slab. By fitting a third-order Birch-Murnaghan equation of state to our compression data, we obtained a bulk modulus KT0=298(7) GPa with K′ = 4.3(5). With K′ fixed to a value of 4, the bulk modulus KT0=304(3) GPa. Our results indicate that Al3+ and H+ have a small effect on the elastic properties of stishovite. Compared with data obtained up to 43.8 GPa, peak intensities changed and we observed a decreased quality of fit to a tetragonal unit cell at pressures of 49 GPa and higher. These changes may be an indication that the rutile↔CaCl2 transition occurs between these pressures. After laser annealing of the sample at 58.3(10) GPa and subsequent decompression to room conditions, the cell volume is the same as before compression, giving strong evidence that the composition of the recovered sample is also unchanged. This suggests that Al and H are retained in the sample under extreme P-T conditions and that stishovite can be an agent for transporting water to the deepest lower mantle.
AB - We have determined the P-V equation of state of Al-rich H-bearing SiO2 stishovite by X-ray powder diffraction at pressures up to 58 GPa using synchrotron radiation. The sample contained 1.8 wt% Al2O3 and up to 500 ppm H2O, and had a composition that would coexist with Mg-silicate perovskite in a subducted slab. By fitting a third-order Birch-Murnaghan equation of state to our compression data, we obtained a bulk modulus KT0=298(7) GPa with K′ = 4.3(5). With K′ fixed to a value of 4, the bulk modulus KT0=304(3) GPa. Our results indicate that Al3+ and H+ have a small effect on the elastic properties of stishovite. Compared with data obtained up to 43.8 GPa, peak intensities changed and we observed a decreased quality of fit to a tetragonal unit cell at pressures of 49 GPa and higher. These changes may be an indication that the rutile↔CaCl2 transition occurs between these pressures. After laser annealing of the sample at 58.3(10) GPa and subsequent decompression to room conditions, the cell volume is the same as before compression, giving strong evidence that the composition of the recovered sample is also unchanged. This suggests that Al and H are retained in the sample under extreme P-T conditions and that stishovite can be an agent for transporting water to the deepest lower mantle.
KW - Equation of state
KW - High pressure
KW - Synchrotron X-ray diffraction
KW - Water in the mantle
KW - Water-bearing stishovite
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U2 - 10.1007/s00269-005-0016-3
DO - 10.1007/s00269-005-0016-3
M3 - Article
AN - SCOPUS:28044462397
SN - 0342-1791
VL - 32
SP - 466
EP - 470
JO - Physics and Chemistry of Minerals
JF - Physics and Chemistry of Minerals
IS - 7
ER -